This walkthrough covers Atlantica in Kingdom Hearts Final Mix, including the route to the Sunken Ship, both Ursula battles, and sealing the world’s Keyhole. The key progression points are moving the dolphin to the Undersea Valley, using the cauldron to expose the first Ursula, and equipping Mermaid Kick after that fight to cross the current to Giant Ursula.
Atlantica route at a glance
- Catch up with Flounder, defeat the Heartless, then follow the trident markers to Triton’s Palace.
- Visit Ariel’s Grotto. Take the Torn Page from the chest if you want to advance the Hundred Acre Wood book.
- In the Undersea Gorge, grab onto the dolphin for several seconds and release it so it moves to the Undersea Valley.
- Use the Undersea Cave and Calm Depths route to reach the Undersea Valley, then take the dolphin toward the Sunken Ship.
- Collect the Crystal Trident, trigger the story sequence at Ariel’s Grotto and Triton’s Palace, and return to the ship to open the passage to Ursula’s Lair.
- Defeat Ursula at the cauldron, equip Mermaid Kick, and swim against the current from Calm Depths into the cave marked ???.
- Defeat Giant Ursula, then return to Ariel’s Grotto to seal the Keyhole.
How to reach the Sunken Ship
Move the dolphin to the Undersea Valley
After the early sequence with Flounder and the Heartless, follow the trident markers to Triton’s Palace, then visit Ariel’s Grotto. In the Undersea Gorge, hold onto the dolphin for several seconds and let go. It will move to the Undersea Valley, where you can use it to continue toward the Sunken Ship.
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If you cannot find it, return by way of the Undersea Cave and Calm Depths and check the Undersea Valley. A purple sea urchin in Calm Depths can be hit with Fire to reveal an opening in the wall to the valley.
Get the Crystal Trident and open Ursula’s route
At the Sunken Ship, take the Crystal Trident from the chest near the far window. A shark encounter occurs around this part of the sequence; defeat the shark at least once before trying to reach Ursula’s Lair.
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Return to Ariel’s Grotto and activate the blue trident symbol, then go to Triton’s Palace. After Ursula takes Triton’s trident, head back to the Sunken Ship and examine the white panel on the far wall. Sebastian opens the passage. At the fork, the right-hand path reaches Cavern Nook and its save point; take the left path toward Ursula.
How to beat Ursula the first time
This encounter is built around the cauldron, not repeated direct attacks on Ursula. Lock onto the cauldron and cast magic after Ursula throws a potion into it. Fira can be an efficient choice, but no particular spell or fixed number of casts is required. In the KHGuides walkthrough, the cauldron’s color signals the attack coming next; it is not a cue to match the color with a spell element.
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- Wait for Ursula to throw a potion into the cauldron.
- Cast magic at the cauldron until it erupts.
- While Ursula and the eels are dazed, attack Ursula with the Keyblade.
- Retreat when she recovers and spins, then repeat the cauldron setup.
If you need MP, use Ethers or hit the eels. After the victory, you earn Mermaid Kick, the ability needed for the next route.
How to cross the current to Giant Ursula
Open the shared abilities menu and equip Mermaid Kick. Return through the Sunken Ship to Calm Depths, then repeatedly use the ability to swim against the jet stream leading to the cave marked ???. Without Mermaid Kick equipped, the current blocks the way forward.
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How to beat Giant Ursula
Giant Ursula is a separate fight: keep moving, and attack her face during brief openings. The main danger is staying in front of an attack instead of creating space or changing direction.
- When she inhales: swim away from her mouth to avoid being pulled in.
- When bubbles appear: swim upward or sideways to get clear.
- When she fires a beam from her mouth: move laterally rather than staying in its path.
- When her health is around half: her lightning sequence becomes more dangerous. Respond to the warning cue and create distance.
Aero can reduce incoming damage, and Stop may briefly interrupt her movement or attacks; both are optional tactics. Keep looking for openings to hit her face rather than trying to trade hits.
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Seal Atlantica’s Keyhole
After defeating Giant Ursula, return to Ariel’s Grotto with the Trident to seal the Keyhole. The KHGuides walkthrough lists Thundara, Ansem Report 3, and the Crabclaw keychain among the rewards or follow-up outcomes. Reward details can differ by release, so this list is specific to that guide’s version coverage, not a guarantee for every Kingdom Hearts game featuring Atlantica.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How the two Ursula fights differ
| Encounter | Main mechanic | Survival response | Progression outcome |
|---|---|---|---|
| Ursula | Activate the cauldron with magic, then attack while she is dazed. | Retreat when she recovers and spins. | Victory awards Mermaid Kick, which enables the route through the current. |
| Giant Ursula | Attack her face during openings. | Stay mobile; evade the inhale, bubbles, beam, and more dangerous lightning sequence. | Victory lets you return to Ariel’s Grotto and seal the Keyhole. |
Useful combat note for underwater encounters
Physical attacks can be harder to rely on underwater. The KHGuides walkthrough recommends offensive magic such as Fire, Blizzard, and Thunder for the Heartless encounters; use the spell that fits your available magic and MP.
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